The present invention relates to a vertical take-off aircraft.
Vertical take-off aircraft are known especially for military purposes wherein a jet engine is located within the main fuselage between the wings and has a plurality of complexly controlled swivelable nozzles which direct the hot air thrust downwardly during vertical take-off and landing and swivel for forward and reverse flight.
It is also known to provide an aircraft wherein the ends of the wings carry propellers which are displaceable from a take-off position wherein the propellers rotate about a substantially vertical axis to a horizontal position for normal flight although considerable difficulties have been experienced in controlling the aircraft when effecting the transition from one position to the other.
A professor Paul Moller has been developing flying cars since 1963 and currently proposes using eight small jet engines and where the thrust is deflectable from horizontal to vertical directions and vice versa but such does not have wings.
Other proposals using multiple jet engines, even some without aerofoils/wings, have been proposed and such are expensive, complex, noisy and produce a hot air blast which can be damaging to the surroundings.
It is an object of the present invention to provide a vertical take-off personal aircraft which is economical and simple to produce with acceptable noise output and without the use of hot air jets for landing.
According to the present invention there is provided a vertical take-off and vertical landing aircraft comprising an aircraft body or fuselage having at least one wing or aerofoil means extending either side of the fuselage or integral therewith to provide lift for the aircraft with forward movement, a normally vertically or substantially vertically extending main air duct extending through the fuselage having at least one air inlet at the top and at least one air outlet at the bottom, an impeller or fan means located in said duct and operable to create a downward flow of air and comprising two oppositely or contra-rotatable impellers or fans driven to rotate about a vertical or substantially vertical axis within said duct and wherein air is directed to air distribution or air-directing means located beneath the rotary impeller or fan means, said distribution means causing some of the air-flow to flow through wing ducts extending to extremities of the wings and exiting in a downward direction and located in spaced apart regions in each wing or on the side of the fuselage to optimize stability, and a rear air duct leading to the rear of the fuselage with an air outlet for optionally contributing to forward propulsion and directional control, and at least one engine connected to drive said rotary impeller or fan means and preferably located beneath the normal level or substantially beneath the normal horizontal plane or level in which the wing outlets lie so as to contribute to the stability of the aircraft, and control means for controlling air deflection at the outlet of each of the wing ducts and of the bottom outlet duct and the rear outlet when provided. Preferably a single, high powered engine will be provided although for longer range for city-to-city travel, for example, an additional rear thrust drive may be achieved by means of an additional engine such as a dedicated jet engine.
Preferably the aircraft pilot (and any passenger) will sit in a balanced position forwardly of the impeller duct and as low down as possible relative to the centre of gravity of the aircraft and the air outlets in the wing.
Preferably the outlets in the wing and the outlet at the bottom will have air deflection means such as a plurality of parallel normally horizontally disposed deflector blades or foils pivotable about substantially horizontal axes and displaceable together somewhat in the manner similar to that of a louvre window so as to enable the flow of air therepast to be directionally adjusted and controlled so that transition from vertical direction to forward direction is possible by deflecting the air stream rearwardly and vice-versa. Similarly, horizontally disposed pivotal deflectors may be controllably locatable in the rear outlet duct for upward and downward directional control.
Preferably the vertical air ducting means, for efficiency, will have a lower part beneath the impeller means and a lower converging central portion leading to a, preferably, elongate rectangular slot and in which air deflectors are located with the main axis of the slot i.e. the longer sides, running fore and aft relative to the extension of the fuselage in the normal direction of forward travel.
Preferably the lower part of the main air duct forms the air distribution means and includes a rear air duct running from the normally rear side of said converging central portions when provided to the rear air outlet and preferably the lower part is divided by a baffle wall centrally transverse to the fuselage and has an optionally displaceable flap or deflection or closure means associated therewith and operable so as to deflect some air as desired instead of going downwardly for vertical lift, but rather so as to flow rearwardly to the rearwardly directed air duct to supplement the forward propulsion and/or left and right movement control and possibly also the upward and downward movement control. Around a flow-dividing wall of lower part which preferably comprises an the outer upper cylindrical wall portion of said central duct, there is an outer, preferably concentrically located, cylindrical duct-defining wall having diametrically opposite outlet passages for the flow of air to the wing ducts on either side and forming part of the air-flow distribution means.
Also to ensure a smooth and efficient and equal division of air to the ducts in both wings, the space between the inner and outer concentric cylindrical walls forming the wing duct air-flow take-off part of the distribution means is divided either side of a diametrical line preferably extending in fore and aft direction and preferably by deflection chutes- running gradually downwardly, closing-off the space between the cylindrical walls somewhat in the appearance of a helter-skelter chute with the chute walls running downwardly and inclined outwardly and leading to openings in the outer cylindrical walls connected to the wing air-flow ducts and wing outlets.
The impellers or fan blades are preferably arranged to be contra-rotating so as to cancel out any torque effect and to avoid the need for a tail rotor as used on helicopters which stops the fuselage rotating although other means for fuselage directional control may be provided if contra-rotation is not desired.
For regions of the body of the fuselage provided for aesthetic and aerodynamic purposes which create cavities therebeneath, such may be sealed or filled with expanded foam material or the like so that such acts as flotation means so that the aircraft can float on water - i.e. a filed double skin arrangement can be provided.
The body of the aircraft is preferably made of carbon fiber.
The engine will importantly have to be a high powered engine and lightweight.
Suitable control means, which may be a computer control, are provided for balancing and controlling the airflow deflector members and engine etc.
It will be appreciated that the present invention provides an aircraft which is quiet to operate and simple to produce and utilises cold air propulsion without hot air jets in the take-off and landing mode. In the event of engine failure with the aircraft having a vertical axis rotor or turbine or impeller, landing conventionally only using the extra lift from the wing is possible. The centralised thrust provides a stable arrangement which is more readily controllable especially in the transition from vertical movement to horizontal movement. The wings of aerofoil section, of course, provide a lift effect in forward motion.
It is considered that hitherto the most difficult problem to overcome was the transition from vertical lift-off to horizontal flight and vice-versa.
Further in respect of prior aircraft, the necessary power to weight ratio has only normally been possible with military jet engines since a dead lift is a difficult requirement.
In every case hitherto the flight transition problem has been responsible for delays in development beyond what might have been expected and in fact delaying development for years.
To solve this problem it has now been realised that one should avoid the hitherto mistake of rotating 100% of the lifting force (engine) and expecting the aircraft to remain stable.
The present invention enables the main thrust to be kept vertical with only a slight shift of thrust until forward momentum has been attained, further stability being maintained from the wingtips.
The control means are to be such that at no time can the pilot move the controls to override the thrust sequence to maintain stability until it is in the flying mode excepting to prolong vertical take-off i.e. by manually holding-on but automatic controls limit the time in these modes and will then cycle to fly.
One cause of the great lack of stability of VTOL aircraft in past models has been because the wings are in the same plane as the engines.
The present invention provides for stability by a configuration with a low centre of gravity because of the engine location is as it were a ships"" keel and it is also intended in some embodiments, the aircraft might float and take-off from water.
The present invention provides a new and inventive combination which hitherto had not been considered in the design of aircraft or, if it might have been, would likely have been discarded since the idea of using an air duct extending from the top to the bottom of an aircraft with the inlet to the duct being upwardly open at the top would not have considered operable because of the anticipated loss of intake of air as would result during forward movement of the aircraft since it would be expected that the loss of induced air would incur because air would pass directly over the air inlet. If one envisages that perhaps 500,000 cubic feet of air would be required to lift an aircraft, half would be expected to be lost upon forward movement. However, the inventive concept of the present invention utilises the realisation that with forward movement of the aircraft, lift occurs as a result of the air flowing over the aerofoil sections which means that the volume of downwardly directed air can be reduced by reducing the hitherto required high revolutions per minute required of the engine for lift which revolutions are no longer required for forward movement and thus any loss of inlet air because of air passing over the top of the inlet duct as a result of forward motion becomes unimportant since such is compensated for by the aerofoil lift effect and the possibility to reduce the revving of the engine with a reduction in intake requirements for upward lift by the down thrust. The provision of the rear propulsion enhances its forward movement and flight.
In hovering flight, high power is used but no forward flight is achieved. The thrust/weight ratio required for control, lift and manoeuvring whilst hovering is around 1.4 while the lift/drag in cruising flight may be around 10 say and the equivalent cruising thrust/weight is 0.1.
It will be seen that the energy required for normal flight is minimal compared to VTO resulting in the contra rotating impellers being almost at idle during flight, but are still able to supply all the air that is required for the rear impellers to draw from with aid of the deflector.